Cosmological meaning of the gravitational gauge group

TL;DR

This paper investigates a specific gravitational model with torsion, showing it can replace the big bang singularity with a big bounce, and links it to a de Sitter gauge group via a Kaluza-Klein-like approach.

Contribution

It identifies the unique model with nonvanishing torsion effects in a cosmological setting and connects it to the de Sitter gauge group through a novel ansatz.

Findings

Only the beta=1/2 model has nonvanishing torsion effects in the Robertson--Walker universe.

The torsion effect can replace the big-bang singularity with a big bounce.

The model can be derived from a de Sitter gauge group using a Kaluza-Klein-like ansatz.

Abstract

It is shown that among the R+beta S^{abc}S_{abc} models, only the one with beta=1/2 has nonvanishing torsion effect in the Robertson--Walker universe filled with a spin fluid, where S_{abc} denotes torsion. Moreover, the torsion effect in that model is found to be able to replace the big-bang singularity by a big bounce. Furthermore, we find that the model can be obtained under a Kaluza--Klein-like ansatz, by assuming that the gravitational gauge group is the de Sitter group.